VMware Depot

Friday, June 29, 2012

vSphere APIs for Array Integration (VAAI) is a set of features introduced in vSphere 4.1, which allow for offloading certain storage related tasks (e.g. VM cloning, disk zeroing etc.) from VMware hosts to the storage systems. VAAI is included in vSphere Enterprise and Enterprise Plus licensing and enabled by default on ESXi 4.1 and later hosts , but in order to work properly, VAAI also needs to be supported by the underlying storage system (usually achieved through a storage firmware update).

There are some setups in which it is recommended to completely disable VAAI - e.g. when using an EMC RecoverPoint fabric splitter or EMC CX4 array with vSphere 5. This blog post describes how to disable the three base VAAI features from vSphere 4.1, as well as "Space Reclamation" (SCSI UNMAP) feature introduced in vSphere 5. Disabling VAAI is done on a per-host basis and doesn't require host restart.

Disabling SCSI UNMAP

This is a new VAAI feature introduced in vSphere 5, which allows for reclaiming space on the storage system after a file is deleted from a VMFS datastore. Shortly after vSphere 5 was released, it was determined that this feature can cause problems with certain storage systems and storage vMotion / snapshot creation operations, so VMware recommended disabling it completely (see VMware KB 2007427 - Disabling VAAI Thin Provisioning Block Space Reclamation (UNMAP) in ESXi 5.0).

Since ESXi 5.0 Patch 2 (ESXi build number 515841, released on December 15, 2011) this feature is disabled by default (ESXi 5.0U1 keeps it disabled, but introduces an option to run Space Reclamation manually from the CLI - see VMware KB 2014849), so if you're using ESXi 5.0 with a lower build number, you can either patch your hosts to Patch 2 level, or use the following workaround from the CLI.

Friday, June 8, 2012

Enhanced vMotion Compatibility (EVC) is a feature of vSphere clusters which allows vMotion between hosts with CPUs of different generations (e.g. a host with an Intel Xeon E5520 CPU and a host with an Intel Xeon E5-2630 CPU). If you have hosts with different generation CPUs, properly setting EVC is a prerequisite for adding these hosts to the same cluster. Setting EVC on a cluster basically forces CPUs of all hosts in the cluster to use a common baseline - a set of instructions which is compatible with all CPUs in the cluster.

EVC is a vSphere feature that can be enabled regardless of vSphere license edition you're using. It can be enabled on a cluster by right clicking on a cluster in your inventory -> Edit Settings -> VMware EVC -> Change EVC Mode.

This KB article is the best possible EVC reference in which you can find which EVC cluster baselines are supported by different CPU models. All you need to do is find the (not required but recommendedhighest) baseline which is supported by all of your host CPUs and configure EVC to work in this mode. Although you can choose any baseline supported by all CPUs, it is recommended to choose the highest baseline, because of reasons described at the end of the post. For example, if you need to create a cluster with the previously mentioned E5520 hosts and E5-2630 hosts, you would set "Intel Nehalem Gen." as your EVC mode. The EVC menu can also be of help, because when you choose an EVC mode it will tell you whether the hosts which are already a part of the cluster support that EVC mode.

There are a few things which you need to have in mind when configuring EVC in an existing cluster:

when EVC is disabled, this is equal to all host CPUs working with the highest supported EVC baseline

if you have a cluster with older hosts (e.g. with E5520 CPUs) with EVC disabled, and you need to add new host(s) to the cluster (e.g. with E5-2630 CPUs), you need to first enable EVC in the proper mode and then add new hosts; this can be done without any disruption - setting a CPU to work with it's highest supported baseline (in this example "Intel Nehalem") can be done with VMs running on the hosts

if you need to add an older host (e.g. a server left after virtualizing a service it used to run) to a cluster with EVC disabled and newer hosts which are running VMs, you will be configuring hosts to work in a lower EVC baseline than they are currently; in order to do this, all hosts in the cluster have to be in maintenance mode, which means that all VMs running on them need to be powered off (or migrated to a different cluster, if possible)

Friday, June 1, 2012

Collecting logs from an ESXi host is a recommended best practice, but if you ever tried to collect ESXi host logs over syslog, you may have noticed that ESXi hosts can be very chatty and spam your syslog server relentlessly.

There are 8 logging levels of the ESXi host agent (hostd) and these are (sorted by the amount of information logged in the increasing order): "none", "quiet", "panic", "error", "warning", "info", "verbose" and "trivia". vCenter agent (vpxa) has 6 logging levels: "none", "error", "warning", "info", "verbose" and "trivia". Default logging levels for both host and vCenter agent in ESXi 5.x is "verbose" and this is the reason why your syslog server is filled with a lot of seemingly useless information.

If you want to change the logging level, fire up your vSphere Client, connect to vCenter/host, select a host in the inventory, then the Configuration tab -> Advanced Settings -> Config -> HostAgent -> Log. Here you'll be able to review all logging levels for hostd and vpxa agents and change logging levels by typing in name of the desired level (hostd) or selecting from a drop down menu (vpxa). This setting takes effect immediately after clicking OK (no host or hostd/vpxa restart is required).

Monday, May 28, 2012

Since virtual machine hardware version 7 (introduced by vSphere 4.0), you may have noticed that VM's network adapter and hard drives appear as one of the devices available for removal when you click the Safely Remove Hardware icon in Windows taskbar. This can cause problems, especially in VDI environments, where users can accidentaly remove VM's network adapter instead of e.g. their USB device, which will result in VM's immediate loss of connectivity and tech support calls.

You can avoid situations like this, if you completely disable virtual machine device hot add / remove. In this way, network adapter and hard drives won't appear in the Safely Remove Hardware menu, but have in mind that setting this option will also prevent you from hot adding / removing ANY device from the VM (network adapter, hard drive, USB controller etc.), which means that you'll have to shutdown the VM in order to add/remove any part of its virtual hardware. CPU / memory hot add/remove is not affected by this setting.

In order to disable VM device hot add/remove, shutdown the VM, right click on it and select Edit Settings, choose Options tab -> General -> Configuration Parameters. Click Add Row and add a row with name devices.hotplug and value false, confirm the setting with a couple of OKs and power on the virtual machine again. The following picture illustrates how your advanced parameters dialog should look like after adding this setting.

Thursday, May 24, 2012

ESXi hosts can be joined to Active Directory, or more precisely can use Active Directory for authenticating users, which allows for assigning permissions to domain users on the host level. This post describes the procedure for joining an ESXi host to the domain through vSphere Client and vSphere CLI, and you can alternatively use Host Profiles or PowerCLI for performing the same task. Unlike for Windows machines, joining ESXi to a domain doesn't require a reboot.

First you need to make sure that your host can reach your domain controllers and resolve the FQDN of your domain, which is commonly accomplished by setting your domain controllers / DNS servers for your domain as the host's DNS servers (select a host in vSphere Client -> choose Configuration tab -> DNS and routing -> Properties -> set Preferred and Alternate DNS server to the appropriate addresses).

Joining host to a domain through vSphere Client

In the host's Configuration tab, select Authentication Services option and then Properties in the upper right corner. From the drop down menu, select "Active Directory" as the Directory Service type, type the FQDN of your domain and select Join Domain as shown in the following picture.

After this, you will be prompted to enter credentials of a domain user with enough privileges to join a computer to a domain (you can do enter the username in <domain FQDN>\<user>, <user>@<domain FQDN> or just <user> format). Alternatively, you can use vSphere Authentication Proxy, which is a new feature introduced in vSphere 5 and represents a server which securely stores credentials for joining AD (commonly used in environments with Auto Deploy hosts so that these credentials don't have to be stored as a part of the Host Profile).

Joining host to a domain through vSphere CLI

You can also join the host to a domain through vSphere CLI. Power up the vSphere CLI on your client machine and type away:

vicfg-authconfig --server=<IP address /DNS name of your host> --username=<username of the administrative user on the host> --password=<password

After you've joined a host to the domain, you may notice a new computer object for the host created in the defaults Computers container in AD. You can move this object to the appropriate OU according to your AD structure, but since ESXi is not a Windows machine, obviously don't expect your Group Policies to apply to it :)

Assigning host permissions to domain users

When a host uses Active Directory for authentication, you can assign host privileges to domain users, which is useful in cases when you e.g. don't have a vCenter server, but only a standalone host (when you have a vCenter server joined to a domain, you can assign vCenter Roles on a host level to them even if your host is not a part of the domain). Connect to your host using vSphere Client, right click your host and select Add Permission. When you select Add in the User and Groups part of the screen, you'll notice that you can choose between local users (marked as (server) in the Domain drop down) and AD users.

Also, when a host is a part of the domain, you can assign Administrator role on a host level to domain members in a very simple way. What you need to do is to create a domain security group called "ESX Admins" (note that it's ESX not ESXi in the name), and all domain users which are members of this group are automatically assigned the Administrator role on the ESXi servers in the domain. These users can also log on to host locally through vSphere Client, SSH or ESXi Shell.

Leaving the domain

If you decide to remove the host from domain and switch back to local user authentication, you can do this through vSphere Client by selecting the host in the inventory, Configuration tab -> Authentication Services, and choosing Leave Domain. Host will then continue to authenticate only locally created users (e.g. root), and you can delete the computer object representing your host from the domain.

Sunday, May 20, 2012

vMotion has been completely rewritten in vSphere 5, and several improvements to the mechanism have been added, including the possibility to saturate 10Gbps links when performing a live migration, as well as improved convergence in cases when virtual machine memory changes faster than the vMotion transfer rate. Complete list of improvements and best practices for vMotion in vSphere 5 can be found in this VMware document - VMware vSphere vMotion Architecture, Performance and Best Practices in VMware vSphere 5.

One of the improvements is also the ability to configure multiple port groups (which are using different uplinks) for vMotion, and the mechanism can now use them simultaneously in order to migrate the VMs, even in cases when only one VM is migrated. In this way, if you have a 1Gbps vMotion network between hosts, you can utilize multiple host NICs for vMotion migration and therefore benefit from improved throughput resulting in faster vMotion migrations (which can be very useful especially in cases when you need to e.g. migrate all VMs from a host in order to perform maintenance tasks).

Configuring vMotion to use multiple host NICs is very simple - you need to create two VMkernel port groups on a virtual switch with different IP addresses and in the appropriate vMotion VLAN, mark them to be used for vMotion (Edit port group settings -> General tab -> mark the Enabled field next to vMotion) and edit their NIC Teaming settings so that they use different vSwitch uplink as the active uplink.

For example, if vmnic0 and vmnic1 are the uplinks of your virtual switch where these port groups are located, and you created port groups vmotion1 and vmotion2, you would configure vmotion1 to use vmnic0 as the active and vmnic1 as the standby adapter, and configure vmotion2 to use vmnic1 as the active and vmnic0 as the standby adapter.

This is how your port group NIC Teaming configuration should look like on the port groups:

These are the two vMotion port groups on the vSwitch:

If you are using distributed switches, you need to create two port groups with the same uplink configuration as described above, create two Virtual Adapters for vMotion on every host and bind them to different port groups previously created on the distributed switch.

The procedures described are for the most common case when you have two uplinks on the management / vMotion vSwitch, but vSphere 5 supports using up to 16 1Gbps or 4 10Gbps uplinks for Multi-NIC vMotion in this way. If you have more than two uplinks available and configure more than two vMotion port groups, all you need to do is configure one uplink to be active per a port group and all the other uplinks as standby.

One word of advice for the end - be sure to isolate vMotion in a separate VLAN/subnet than your Management / IP storage / VM networks if you haven't done that already per VMware best practices, since I've seen cases when performing a vMotion migration in vSphere 5 causes loss of connectivity to the hosts or between the host and iSCSI/NAS storage when the same VLAN/subnet and even port group was used for Management, IP storage and vMotion traffic.

Thursday, May 17, 2012

Since vSphere 5, you can remove the annoying warning that appears on ESXi hosts when you turn ESXi Shell or SSH on. This warning can be seen when selecting host's Summary tab and therefore can't be removed by simply going to the Alarms tab and acknowledging / clearing it.

Both of these warnings can now be removed by going to host's advanced parameters (Configuration tab -> Advanced Settings), selecting UserVars on the left side and setting parameter UserVars.SupressShellWarning to 1.